maximal unilateral leg strength correlates with linear sprint and … · 2013-04-24 · title (in...

Maximal unilateral leg strength

correlates with linear sprint and change

of direction speed

Anton Arin, Daniel Jansson & Kristian Skarphagen

Uppsats/Examensarbete: 15 hp

Program och/eller kurs: Sports Coaching

Nivå: Grundnivå

Termin/år: Vt 2012

Handledare: Jesper Augustsson

Rapport nr: VT12-66

Preface

It is a constant problem for coaches, fitness coaches and strength and conditioning coaches to select

exercises that are best suited for their sports. Earlier research on sports has examined specific

qualities in general training and is now progressing towards more complex and sport specific

qualities. When training for a specific sport, one of the main tasks is to analyze the specific sport in

terms of movement patterns, intensity and which type of strength the sport require. More studies

regarding sports specific training are still required. Sport coaches around the world suggest different

advice for optimal training for a specific sport and it requires scientific research to confirm or reject

the various proposals.

Unilateral (one leg) training is gaining popularity in sports. There are few scientific studies made in

this field today and there is a need for evaluating different unilateral training, such as intervention

studies and correlation studies, to assist sport coaches find exercises with a high transfer value to

each sport. Intermittent sports require different activities such as change of direction, forward and

backward running and lateral stepping ability. Intermittent sports are often performed unilaterally

with the power and force development on one leg at the time, for example in running sports where

one leg at the time is producing push-off acceleration force.

The authors of this study discovered that, despite the increased interest for sport specific training,

research on unilateral resistance training is lacking. We therefore decided to investigate two major

and different intermittent sports in Sweden, soccer and ice-hockey, and the transfer value between

unilateral leg exercises to CODS and linear sprint.

This study have been inspiring and challenging for us and hopefully it will contribute to increased

knowledge on unilateral training. Along the way, we have had good guidance and this we are

grateful for. First of all we would like to thank our participants which made this study possible. We

would also like to thank Jonas Enqvist for useful guidance, interesting discussions and the help with

the testing equipment. Rolf Idegård at Friidrottens Hus for the great hospitality during the testing

procedures. Finally we would like to thank our supervisor Phd. Jesper Augustsson for appreciated

advice and review of the study.

This study was granted by Riksidrottsförbundet (RF).

Best regards

Arin, Anton Jansson, Daniel

Tel: 0736728226 Tel: 0730568128

E-mail: [email protected] E-mail: [email protected]

Skarphagen, Kristian

Tel: 0733447495

E-mail: [email protected]

Abstract

Title (in English) Maximal unilateral leg strength correlates with linear sprint and change of

direction speed

Title (på svenska) Maximal enbensstyrka korrelerar med linjär sprint och snabbhet i

riktningsförändringar

Author (s): Arin, A., Jansson, D. & Skarphagen, K.

Institute: Department of Food and Nutrition, and Sport Science

University of Göteborg

P.O Box 300

S-405 30 Göteborg

SWEDEN

Essay: xx ECTS

Programme/course: Sports Coaching

Level: Basic

Semester/year: Vt/2012

Tutor: Jesper Augustsson

Nr. in serie: xx (ifylles ej av studenten/studenterna)

Keywords: Agility, Change-of-direction-speed, CODS, ice-hockey, intermittent

sports, maximal strength, soccer, sprint, unilateral strength

Date:

Number of pages: 35

Summary: Movement patterns in intermittent sports is influenced by change of direction speed

(CODS) performance (i.e., acceleration and deceleration in short sprints). A cross-

sectional study was used to examine if CODS (modified pro agility test) and linear

sprint (5, 10 and 20 m) correlated with maximal (1RM) unilateral leg strength

(unilateral Smith machine squat and unilateral leg press) and unilateral standing

balance. Twenty youth male college athletes (soccer players n=10, ice-hockey

players n=10, weight 76.8±6.6 kg, height 180.5±5.9 cm, age, 16.6±1.3 years)

performed the tests. A significant (P<0.005) moderately strong correlation between

CODS and normalized unilateral squat strength was found (r = -0.606).

Furthermore, a significant (P<0.003) moderately strong correlation between CODS

and normalized unilateral leg press strength were found (r = -0.631). A significant

(P<0.003, P<0.002, respectively) moderately strong correlation between CODS and

linear sprint (10, 20 m) were found (r = -0.629, r = -0.641, respectively).

Normalized unilateral squat strength had a significant (P<0.015) moderately strong

correlation to 10 m linear sprint (r = -0.534). Normalized unilateral leg press

strength had a significant (P<0.006) moderately strong correlation to 10 m linear

sprint (r = -0.593). Between normalized unilateral squat strength and 20 m linear

sprint there was a significant (P<0.027) moderately low correlation (r = -0.493).

The correlation between normalized unilateral leg press strength and 20 m linear

sprint was significant (P<0.020) moderately strong (r = -0.514). The findings

suggest that unilateral maximal strength testing is a good predictor for CODS and

linear sprint for soccer players and ice-hockey players.

Sammanfattning: Rörelsemönster i intermittenta idrotter är influerat av snabba riktningsförändringar

(CODS) och består till stor del av acceleration, och deceleration under korta sprinter.

En tvärsnittsstudie gjordes för att undersöka om CODS (modifierat pro agility test) och

linjär sprint (5, 10 och 20 m) korrelerade med maximal (1RM) unilateral benstyrka

(unilateral knäböj i Smith-maskin och unilateral benpress) och balans på ett ben. Tjugo

manliga ungdomar på idrottsgymnasienivå (fotbollsspelare n=10 och ishockeyspelare

n=10, vikt 76.8±6.6 kg, längd 180.5±5.9 cm, ålder, 16.6±1.3 år) utförde testerna. En

signifikant (P<0.005) moderat stark korrelation mellan CODS och normaliserad

unilateral styrka i knäböj i Smith-maskin hittades (r = -0.606). Vidare hittades en

signifikant (P<0.003) moderat stark korrelation mellan CODS och normaliserad

unilateral styrka i benpress (r = -0.631). En signifikant (P<0.003, P<0.002, respektive)

moderat stark korrelation mellan CODS och linjär sprint (10, 20 m) hittades (r = -

0.629, r = -0.641, respektive). Normaliserad unilateral styrka i knäböj hade en

signifikant (P<0.015) moderat stark korrelation med linjär sprint (10 m), (r = -0.534).

Normaliserad unilateral styrka i benpress hade en signifikant (P<0.006) moderat stark

korrelation med 10 m linjär sprint (r = -0.593). Mellan normaliserad unilateral styrka i

knäböj och 20 m linjär sprint fanns det en signifikant (P<0.027) moderat låg korrelation

(r = -0.493). Korrelationen mellan normaliserad unilateral styrka i benpress och 20 m

linjär sprint var signifikant (P<0.020) moderat stark (r = -0.514). Resultaten föreslår att

testning av normaliserad unilateral maximal styrka är en bra förutsägning för CODS

och linjär sprint för fotbollsspelare och ishockeyspelare.

Content

1. Introduction ...................................................................................................................................... 1

1.1 Agility and sub-components ....................................................................................................... 2

1.2 Understanding soccer and ice-hockey ........................................................................................ 3

1.3 The relationship between linear sprint and maximal strength .................................................... 4

1.4 The relationship between CODS and linear sprint ..................................................................... 4

1.5 The relationship between CODS and maximal leg strength ...................................................... 5

1.6 The relationship between CODS and balance ability ................................................................. 5

1.7 Limitations in earlier studies ...................................................................................................... 7

1.8 Purpose ....................................................................................................................................... 7

2. Methods ............................................................................................................................................ 8

2.1 Subjects ...................................................................................................................................... 8

2.2 Familiarization............................................................................................................................ 8

2.3 Testing Procedures ..................................................................................................................... 8

2.3.1 SOLEC on a balance disc .................................................................................................... 9

2.3.2 Change of direction speed performance test ........................................................................ 9

2.3.3 Unilateral Smith machine squat ......................................................................................... 10

2.3.4 Unilateral leg press ............................................................................................................ 11

2.3.5 5, 10 and 20 m linear sprint ............................................................................................... 12

2.4 Statistics.................................................................................................................................... 12

3. Results ............................................................................................................................................ 13

3.1 Correlations between CODS and maximal unilateral strength ................................................ 14

3.2 Correlations between CODS and linear sprint ......................................................................... 15

3.3 Correlations between linear sprint and maximal unilateral leg strength .................................. 16

3.4 Comparing correlations between soccer and ice-hockey players ............................................. 17

4. Discussion ...................................................................................................................................... 25

4.1 Correlation between linear sprint and maximal unilateral leg strength .................................... 25

4.2 Correlation between CODS and linear sprint ........................................................................... 26

4.3 Correlation between CODS and maximal unilateral strength .................................................. 27

4.4 Correlation between CODS and linear sprint to unilateral balance ability .............................. 28

4.5 Differences between soccer and ice-hockey ............................................................................ 28

4.6 Limitations................................................................................................................................ 29

5. Conclusion ..................................................................................................................................... 31

References .......................................................................................................................................... 32

Appendix ............................................................................................................................................ 36

1

1. Introduction

Human locomotion needs biological energy production, and two mechanisms to contribute to

produce energy are the aerobic and anaerobic energy systems. These two systems are the opposite

of each other; the aerobic metabolism using oxygen for energy production, while the anaerobic do

not require the presence of oxygen (Ratamess, 2008, Swank, 2008). An example of when the

aerobic system is highly dominant is marathon or triathlon, with the anaerobic energy system

contributing as little as 10-20 %, often using a cyclic movement during a long period of time. An

example of the anaerobic energy systems extreme is Olympic weightlifting, high jumping or 100 m

sprints, with the anaerobic energy system contributing as much as 80-100 % (Knuttgen, 2007).

Intermittent sports such as tennis, basketball, soccer and ice-hockey is often a mixture of aerobic

and anaerobic extremes. These sports have one thing in common; the presence of both energy

systems but with different amount and it is important to construct a needs analysis for every specific

sport (Baechle, Earle & Wathen 2008, Ratamess 2008, Swank, 2008).

Strength and conditioning coaches are thus struggling with specificity in training in intermittent

sports that require both aerobic and anaerobic ability. Which exercises that contribute to the greatest

transfer value, in sports like soccer, ice-hockey, tennis and basketball are still not clear. Intermittent

sports are complex and involve energy contribution from both the aerobic and anaerobic systems,

including activities such as deceleration, acceleration, linear sprint, changes of direction, backward

running and lateral stepping. In these sports, training have traditionally been largely based on the

game itself but new development in strength and speed training have proved to increase sport-

related activities (Chelly et al. 2009, Jovanovic, Sporis, Omrcen & Fiorentini, 2011). As suggested

by Knuttgen (2007) participation in a specific intermittent sport can contribute to improvements in

strength and aerobic fitness, however most commonly improvement in aerobic fitness. A common

misconception according to Knuttgen (2007) is that strength exercises improve aerobic performance

or the opposite. To be able to challenge the aerobic and anaerobic systems, strength and

conditioning coaches have to be aware of these two represent the opposite extremes of a muscular

power continuum. Intermittent sports require both anaerobic and aerobic energy contribution and

training programs must consider the challenge of the time availability for training to be effective.

Resistance training for sports involve three foundational principles: overload, progression and

specificity for the training to be successful. It is important that progressively overload the muscles

to gain increased strength and stimuli development (Baechle & Earle, 2008). Training adaptations

are highly specific and in a higher level of a specific sport, specificity becomes even more

important. The transfer value in training gains can differ greatly even in very similar exercises; the

exercise selection is a main variable when designing training programs (Zatsiorsky & Kraemer,

2006). In intermittent sports the activities are complex and involve changes in speed, deceleration,

acceleration, backward running and lateral stepping etc. Thus the exercise selections need to cover a

lot of different abilities, and strength and conditioning coaches are struggling with and which

exercise contributes to the greatest transfer value to the specific sport. The new development

regarding the relationship between different strength variables and sport specific speed training

could contribute to improvements in intermittent sports. To be able to train effectively it is

2

important to understand different exercises and the transfer value to a sport-specific activity to be

able to use the training time effectively.

1.1 Agility and sub-components A central concept in intermittent sports is agility, which does not have any global definition but is

often described simply as the ability to change direction rapidly (Sheppard & Young, 2006).

Sheppard and Young (2006, p. 922) noted that the classic definition of agility does not cover overall

agility performance and, as a consequence, proposed a new definition for agility as “a rapid whole-

body movement with change of velocity or direction in response to a stimulus”. According to

Sheppard and Young´s model (2006), Figure 1, agility can be broken down into sub-components

comprising of two main qualities, (1) perceptual and decision-making abilities (cognitive) and (2)

change-of-direction speed (CODS) abilities (physical). Within these two main components (Figure.

1), sub-components exist such as visual scanning, leg strength and straight sprinting speed etc. For

developing overall agility performance, strength and conditioning coaches can target improvements

in agility by targeting the sub-components such as straight sprinting speed, leg muscle qualities,

perceptual and decision-making factors, as well as train sport specific agility drills that include all

sub-components.

The speed development in intermittent sports is undergoing a paradigm shift in the sport science

community. Greater emphasizes is being placed not only on acceleration, maximum speed and

speed endurance (Newman, Tarpenning & Marino, 2004) but also on agility (Chaouachi et al. 2009)

performance because it is an important ability in intermittent sports. Agility performance depends

on different factors whereas CODS is a main sub-component. For improving CODS performance

practitioners can focus on technique, straight sprint speed or leg muscle qualities in training. The

relationship between different variables to CODS performance are an important task to develop in

intermittent sports, for an example if a strength exercise contribute to a sport specific drill.

3

Figure 1. Agility and sub-components (Sheppard & Young, 2006). Agility could be described as a

complex ability with two main variables; one cognitive factor (perceptual and decision-making

factors), and one physical factor (change of direction speed).

1.2 Understanding soccer and ice-hockey Soccer and ice-hockey are intermittent sports which involve different activities, irregular movement

patterns and complex load patterns. Elite soccer player cover a distance of 9-12 kilometer during a

game (Mohr, Krustrup, & Bangsbo, 2003, Hoff & Helgerud, 2004) with approximately 1350

activities (Mohr et al. 2003) and perform about 50 powerful turns (Stolen, Chamari, Castagna &

Wisloff, 2005). Soccer is mainly based on the energy contribution from the aerobic system (Hoff &

Helgerud, 2004, Bangsbo, Mohr & Krustrup, 2006), however the anaerobic high intensity running

and sprints are important factors for the outcome of the game. The importance of anaerobic training

is shown in earlier studies, which concluded that professional soccer players perform more high-

intensity running and sprints during a game than amateur level soccer players (Aziz, Mukherjee,

Chia & Teh, 2008, Mohr et al. 2003, Abrantes, Macas & Sampaio, 2004). Linear sprint and high

intensity CODS movements are thus important for soccer players. A high level of CODS

performance in a game could be the difference between, for example, which player is fastest to the

ball.

High intensity movements that require energy from the anaerobic system are essential for success in

intermittent sports. Ice-hockey is a more anaerobic sport (Popadic Gacesa, Barak & Grujic, 2009)

where the players go “all out” for approximately 30-80 seconds consisting of multiple short bursts

of high intensity skating, continual starting and stopping, changing of directions and delivering and

receiving body checks (Montgomery, 1988, Manners, 2004). This is followed by up to 4-5 minutes

of passive recovery (Montgomery, 1988). These activities also require strength, balance and

stability. In competition strength, balance and stability are central abilities for ice-hockey players.

4

Although ice-hockey is performed on ice, a lot of the training is conducted off-ice. Especially in the

offseason, the training consists of a lot of off-ice training because the availability of ice time is

reduced. It is important that the off-ice measures are capable of predicting specific on-ice

performance for effective training (Farlinger, Kruisselbrink & Fowles, 2007). Studies have

examined correlations between off-ice and on-ice variables (Behm, Wahl, Button, Power &

Anderson, 2005, Potteiger, Smith, Maier & Foster, 2010, Farlinger, et al. 2007). Farlinger et al.

(2007) examined 35 ice-hockey players and found a significant correlation between on-ice 35 m

sprint and off-ice testing (30 m sprint, r = 0.78 and Edgren side shuffle, r = 0.55). Another study

(Behm et al. 2005) on 30 junior hockey players also found a significant correlation between

maximum skating speed and both 40 yard sprint (36.7 m, r = 0.51) and balance ability (wobble

board test, r = 0.51). The authors concluded that off-ice testing could have some cross-over effects

on skating speed and that balance is an important ability for ice-hockey players (Behm et al. 2005).

With this in mind, it is important that off-ice training is effective and sport specific, making it a

better predictor and thus a higher transfer value to specific on-ice performance. Off-ice training is a

part of an ice-hockey player regular training and it is important that off-ice training contribute to

ice-hockey specific movements and these studies (Behm et al. 2005, Potteiger et al. 2010, Farlinger

et al. 2007) shows that there exists a relationship between off-ice training and on ice training.

1.3 The relationship between linear sprint and maximal strength Studies have tested more complex strength exercises such as maximal back squat strength

bilaterally (on two legs) and noted a strong relationship with linear sprints between different

distances (Wisloff, Castagna, Helgerud, Jones & Hoff, 2004, Ronnestad, Kvamme, Sunde &

Raastad, 2008, Chaouachi et al. 2009, McBride et al. 2009, Chelly et al. 2009, Chelly et al. 2010).

McBride et al. (2009) examined 17 division 1-AA male football athletes and the relationship

between maximal bilateral back squat strength (70° between femur and tibia) strength and linear

sprint times and found a significant correlation between normalized back squat strength and 40 yard

linear sprint times (r = -0,605) and 10 yard linear sprint times (r = 0.544). Wisloff et al. (2004) also

reported a significant strong correlation between maximal bilateral half squat strength (90° between

femur and tibia) and 10 m and 30 m linear sprint performance (r = 0.94, r = 0.71, respectively)

when examining 17 elite soccer players.

1.4 The relationship between CODS and linear sprint Studies have examined the relationship between CODS and different variables, for example linear

sprint, strength and balance tests. Earlier studies have focused in particular on correlation between

CODS and linear sprint, but it appears to have little or no influence on CODS (Sheppard & Young,

2006, Little & Williams, 2005, Chaouachi et al., 2009, Wisloff, Castagna, Helgerud, Jones & Hoff,

2004). Little & Williams (2005) examined the relationship between CODS (a zigzag test) and 10 m

and 20 m linear sprint in 106 professional soccer players and found low correlations (CODS and 10

m, r = 0.35 and CODS and 20 m, r = 0.46 and 10 m and 20 m, r = 0.62). The authors concluded that

acceleration and maximum speed and agility were unrelated and thus specific qualities. It therefore

seems as if more specific training is required to develop CODS and that there is a need for more

research on different physical variables (e.g. strength) and their transfer value to CODS

performance.

5

1.5 The relationship between CODS and maximal leg strength Leg strength is considered to be an important part of CODS performance (Young, James &

Montgomery, 2002), however, recent studies have not been able to find a significant correlation

between maximal leg strength and CODS performance (Markovic, Sekulie & Markovic, 2007,

Markovic, 2007, Young et al. 2002, Kapidziv, Pojskic, Muratovic, Uzicanin & Bilalic, 2011).

Young et al. (2002) examined the relationship between concentric leg muscle power and sprinting

speed with changes of direction and found mostly low correlations between concentric leg muscle

power and CODS, while CODS had a significant moderate correlation with reactive strength.

Markovic (2007) examined the relationship between leg extensor strength and power and CODS

performance and found that leg extensor strength and power measures were poor predictors of

agility, however the highest relationship with each of the agility tests were the one-leg rising test (r

between -0.3 and -0.44) suggesting that a functional complex exercise performed unilaterally (on

one leg) was a better predictor of CODS compared with other strength tests. As mentioned earlier,

Wisloff et al. (2004) reported a significant correlation between maximal bilateral back squat

strength and linear sprint but the relationship between maximal bilateral back squat strength and a

CODS test (10 m shuttle run, r = 0.68) was lower, suggesting that other qualities effects CODS

performance besides maximal bilateral leg strength.

Young et al. (2002) examined the relationship between isokinetic unilateral leg extensor power

output and reactive strength with a drop jump. The results revealed that reactive strength between

the right and left leg was correlated to CODS. The participants were significant slower in the

weaker leg in a CODS sprint test.

1.6 The relationship between CODS and balance ability Yaggie and Campbell (2006) examined the effects of a four week balance training program on

functional exercises. 36 recreationally active participants attained the study and were randomly

placed in an experimental and in a control group. The experimental group trained unilateral balance

in different exercises on a BOSU ball. Pretest and posttest consisted of a CODS test (shuttle run)

and functional tasks (time on ball-test performance and vertical jump height). The results revealed

that the experimental group increased significant in the time on ball-test and CODS but not in

vertical jump. Unilateral balance training could be used in a training program for increasing sports-

related activities.

6

Table 1. Summary of recent research of correlation studies between CODS and different predictors.

Reference Sample size CODS test Predictor Results

Young et al. 15 (male soccer, 8-m sprint with bilateral and unilateral Participants who

(2002) tennis, basketball, different changes isokinetic squat and turned faster to one

Australian football of direction DJ side tended to

players) have greater leg

strength in the same

leg in DJ

Thomas & Little 106 (professional Zigzag agility test LS10m, LS20m Significantly

(2005) soccer players) moderately low

correlations

between CODS and

LS10m and LS20m

(r = 0.346 and r = 0.458)

Markovic (2007) 76 (male physical lateral stepping, isoinertal squat, highest relationship

education students) 20-yard shuttle run, isometric squat, between one-leg rising

slalom run one-leg rising, and CODS (r = 0.33,

squat jump, 0.44 and 0.35)

hopping power,

standing long jump

Chaouachi et al. 14 (elite male basket- T-test bilateral 1 RM squat significant relationship

(2009) ball players) (free weights), LS5m, between T-test and 5JT

LS10m, LS30m, SJ, (r= -0.61)

CMJ, Bench, 5JT

LS5m = Linear Sprint 5 m, LS10m = Linear Sprint 10 m, LS30m = Linear Sprint 30 m, SJ = Squat Jump, CMJ= Counter Movement Jump, 5JT = 5

jumping test and DJ = Drop Jump

7

1.7 Limitations in earlier studies CODS involve complex activities and the movements in intermittent sports are often performed on

one leg at a time (Manners, 2004) and consequently unilateral lower limb training should be a good

predictor of CODS. Brughelli, Cronin, Levin and Hansen (2008) concluded that resistance training

and tests should mimic more closely to every specific sport to be a better predictor of change-of-

direction speed (CODS). Most of the earlier studies examining the relationship between strength

and CODS has reported a small sample group (Young et al. 2002, Chaouachi et al. 2009), lower

body bilateral strength (Wisloff et al. 2004, Chaouachi et al. 2009) and no familiarization

(Chaouachi et al. 2009, Wisloff et al. 2004). Altough intermittent sports often require unilateral leg

strength during game performance, earlier studies have tested strength bilaterally (Wisloff et al.

2004, Chelly et al. 2009) The rationale for the present study is that we believe tests preferably be

carried out on one leg at the time to mimic sports that demand unilateral leg strength more closely.

As suggested by Markovic (2007) balance and complex unilateral lower limb strength training

might be important abilities in CODS performance. Earlier studies (Markovic, 2007, Brughelli et

al., 2008) suggested there is a need for more studies on specific exercises and tests that mimic

performance of particular sports in a more realistic way.

1.8 Purpose Since this research area is rather new, according to the authors, this is one of the first studies to

examine the relationship between maximal unilateral leg strength and CODS, performed by youth

male soccer and ice-hockey players. The purpose with the study was to examine the relationship

between CODS to unilateral leg balance and maximal (1RM) unilateral leg strength and in

normalized strength (mean strength for right and left leg divided with body mass) and linear sprint

in youth soccer and ice-hockey players. Another purpose was to examine the relationship between

linear sprint and maximal (1RM) unilateral leg strength and unilateral balance ability for youth male

soccer and ice-hockey players. The same relationships were also tested when soccer and ice-hockey

players were separated. Our research question was as following:

1. Examine the relationship between CODS to maximal (1RM) unilateral leg strength and

normalized strength, unilateral leg balance ability and linear sprint for the total group.

2. Examine the relationship between linear sprint to maximal (1RM) unilateral leg strength and

normalized strength and unilateral leg balance ability for the total group.

3. Examine the relationship between CODS to maximal (1RM) unilateral leg strength and

normalized strength, unilateral leg balance ability and linear sprint for the soccer and ice-hockey

groups separated.

4. Examine the relationship between linear sprints to maximal (1RM) unilateral leg strength and

normalized strength and unilateral leg balance ability for the soccer and ice-hockey groups

separated.

The expected findings of this study could contribute to the understanding of the importance of

specificity in resistance training and testing soccer and ice-hockey players. The hypotheses were

that maximal unilateral leg strength would correlate significant with CODS and linear sprint and

that unilateral balance have a weak relationship with all the selected exercises. CODS and linear

sprint was hypothesized to correlate poorly.

8

2. Methods

This is a quantitative study with a cross-sectional–design, where the participants were selected

through a mix of convenience sample groups, stratified and typical sampling.

2.1 Subjects Twenty youth male soccer players (n=10, age: 17.6±1.0 years; body weight: 77.1±7.4 kg; height:

180.7±7.3 cm) and ice-hockey players (n=10, age: 15.6±0.5 years; body weight: 76.5±6.1 kg;

height: 180.4±4.5 cm) volunteered to participate, after having signed an informed consent form and

read information documents (Appendix 1 and 2) on the study. In the informed consent form the

participant were promised their personal data would be handed with confidentiality, and the

participant could choose to cancel the study at any time. The documents explained the background,

risks, purpose and the procedure of the study. The inclusion criterions were the subjects had to be

youth males between 15-19 years of age, active in ice-hockey or soccer at a sport school at college-

level or an elite level sports team and have experience in resistance training. The participant was

instructed not to conduct any strenuous leg training the day before the testing procedures. The

exclusion criterions were absence of injuries or sickness during the tests. The goaltenders in neither

of the sports were excluded because of the unique physiological demands of their position (Green,

Pivarnik, Carrier, & Womack, 2006, Burr et al. 2008). Five elite sport organisations were contacted

to be a part of the study. Of five organisations asked, two accepted.

2.2 Familiarization The participant attended a familiarization session one week before the actual tests were performed,

to eliminate learning effects. The order of the test battery during the familiarization session was in

the same order the participant were going to conduct the tests one week later. During the

familiarization sessions the test leaders were able to estimate approximately how strong each

participant were in each strength exercise. By performing a familiarization session it was thought

the numbers of 1RM trials during the actual strength tests to be reduced.

2.3 Testing Procedures To evaluate the relationship between maximal (1RM) unilateral leg strength and unilateral leg

balance ability with CODS and linear sprint, a battery of a total of five tests was chosen. The

following tests were included: modified pro agility test (5-10-5 m), a modified SOLEC test

(Standing One Leg Eyes Closed) performed on a balance disc, a maximal unilateral squat test

performed in a standard Smith machine, a maximal unilateral leg press and a linear sprint test (5, 10

and 20 m). The first two sessions consisted of a familiarization session to eliminate learning effects,

one for the soccer group and one for the ice-hockey group, respectively. After the two

familiarization sessions the ice-hockey group and the soccer group was divided in two with five

participants in each group, and had one test session each one week after the familiarization session.

The testing area was located in an indoor running track and the test was completed with the subjects

wearing training shorts, t-shirt and indoor shoes. All the test sessions were performed in the

morning. The sequence of the tests according to Harman (2008) was as following; weight and

height measurement, modified SOLEC on a balance disc, modified pro agility test (5-10-5 m), a

unilateral Smith machine squat, a unilateral leg press and linear sprint (5, 10 and 20 m). The tests

9

started with a 15 minutes warm-up, including running and dynamic stretching. During the tests no

verbal encouragement was given to the subjects. A stop watch was used to ensure the right length of

the rest periods depending on the test. Before the tests were performed, the participant were

weighed and measured; only wearing shorts and t-shirts and no shoes.

2.3.1 SOLEC on a balance disc

The modified SOLEC test (Figure 2) was a balance test that required the subjects to stand on one

leg on a BOSU-ball (Both Sides Up) (height 20 cm, width 62 cm). The other leg was held in 90°

flexion of the knee joint and the arms of the participant were crossed, hands resting on the

acromion. The aim for the participant was to stay in position on the ball as long as possible without

breaking any of the above mentioned criterions. The participant was given two trials per leg, where

the best time on each leg was documented using a stopwatch. The rest interval between each trial

for each leg was at least two minutes.

Figure 2. Modified SOLEC-test (on BOSU ball). The participant was instructed to stand on one leg

for as long as possible with eyes closed and the resting leg at a 90° knee flexion. The arms were

crossed, with the hands resting on the acromion.

2.3.2 Change of direction speed performance test

A modified pro agility test, Figure 3, (Harman & Garhammer, 2008) was used to measure CODS

performance. This test requires acceleration, deceleration and changing the direction of the

participant by rotating the body 180° (Markovic, 2007). The test course started with a 5 m sprint in

a straight line followed by a 180° turn, a 10 m sprint followed by a 180° turn and ended by a 5 m

sprint. The test was conducted with a flying start, 50 cm behind the starting line. The 50 cm were

marked with tape. A computerized system (MuscleLab, Ergotest Technology, Norway) was used to

measure CODS performance. Timing gates were used at the starting/finish line and at every five m

to record every participant performed the test correctly. The participant had two trials with a five

minute rest period between the two trials. The best time was documented. The participant were

10

instructed to run the course as fast as possible and in every 180° turn, face towards the same

direction so both left and right leg performed a turn.

Figure 3. Modified pro agility test. The test started with a 5 m sprint, made a 180° turn and a 10 m

sprint followed by a 180° turn and finished with a 5 m sprint. The participant was instructed to run

the course as fast as possible and in every 180° turn, face towards the same direction so both left

and right leg performed a turn.

2.3.3 Unilateral Smith machine squat

Maximal strength, one repetition maximum (1RM) was measured with a unilateral squat (Figure 4)

in a standard Smith machine which has been validated by Tagesson and Kvist (2007). The unilateral

squat was performed in a standard Smith machine (Nordic Gym, Bollnäs, Sweden), and the

additional weights that were used were standard training discs (Eleiko, Halmstad, Sweden). A

conventional Smith machine consists of a barbell that is fixed within steel rails, which only allow

for vertical movement. When performing the unilateral squat, the participant stood erect and

thereafter performed an eccentric movement to a required 90° angle of the knee joint (between

femur and tibia, A in Figure 4) of the anterior leg. The participant then performed the concentric

phase back to full extension of the knee joint. The squat depth of every trial was standardized with a

goniometer and an elastic exercise band (Thera-band, Akron, USA). When reaching 90° angle in

the knee joint, the participant had to touch an exercise band (B in Figure 4) with m. gluteus

maximus before beginning the concentric phase. The exercise band was set parallel to the floor on

the squat rack behind the participant, and its height was changed, depending on each individual’s

90° knee angle. Both legs were tested, one leg at the time with three minute rest period before the

next trial. The weights were increased with 2.5-10 kg until failure.

11

Figure 4. Unilateral Smith machine squat. When the anterior knee joint was at 90° as required (B)

and m. gluteus maximus touched the exercise band (A), the participant was allowed to begin the

concentric phase of the squat.

2.3.4 Unilateral leg press

Maximal strength of leg extensor muscles was measured by 1RM in a customized leg press

performed unilaterally, as described by Baechle & Earle (2008). The participant was instructed to

lower the machine foot platform in a controlled movement until the thighs were parallel with the

machine foot platform, and on signal from the test leader the test person pushed the weight to full

extension in the knee joint. Both legs were tested, one leg at the time followed by a three minute

rest period before next trial. Since each participant had attended a familiarization session, the

approximate value of 1RM was known in advance. It required no more than 4-5 lifts in order to

assess 1RM. The weights were increased with 2.5-10 kg until failure.

12

2.3.5 5, 10 and 20 m linear sprint

The participant conducted a 20 m linear sprint, where a computerized system (MuscleLab, Ergotest

Technology, Norway) was used to document the time at 5, 10 and 20 m. Timing gates was used at

the starting line, at 5 m, at 10 m and at 20 m which also was the finish line. The linear sprint test

was conducted with a flying start 50 cm behind the starting line. The 50 cm line was marked with a

stripe of tape. The participant performed two trials with a rest period of five minutes between each

trial. The best time was documented. The participant was instructed to run the course as fast as

possible.

2.4 Statistics Statistical analysis was performed using SPSS software (version 20.0, SPSS, Inc, IL). The

significance level was set at P<0.05. Pearson product moment coefficient of correlation was

performed to examine the relationship between each selected variables. According to Thomas,

Nelson & Silverman (2005) a correlation of 0.6 is acceptable and sometimes lower depending on

the research. For this study a Pearson r of 0.0-0.25 was considered low, 0.25-0.50 was considered

moderately low, 0.5-0.75 was considered moderately strong and >0,75 was considered strong.

In addition, the coefficient of determination (r²) was used to examine the amount of explained

variance between tests. The coefficient of determination indicates the part of the total variance in

one measure that can be explained, or accounted for, by the variance in the other measure (Thomas

et al. 2005).

The participants result on left and right leg on unilateral squat, unilateral leg press and modified

SOLEC on a balance disc were documented and summed together. The total sum was divided by

two to present the mean load (1RM mean) and mean time. 1RM mean was also divided with each

participants body mass to get a ratio result for the normalized strength.

13

3. Results

Descriptive statistics (mean ±SD) for all selected variables are depicted in Table 2 including. The

participant (n=20) performed five different unilateral leg tests to examine the relationship to CODS

and linear sprint. The results of the selected tests showed that the mean maximal strength in

unilateral squat was 125.0 ± 22.7 kg and the mean maximal strength in unilateral leg press was

119.2 ± 28.1 kg. The linear sprint tests mean time for 5 m linear sprint was 1.05 ± 0.05 sec, 10 m

linear sprint was 1.78 ± 0.08 sec and for 20 m linear sprint 3.07 ± 0.13 sec. The mean time on the

CODS tests was 4.94 ± 0.15 sec and the mean time for the unilateral leg balance test (SOLEC) was

14.51 ± 22.28 sec.

Table 2. Descriptive statistics (n=20) for maximal unilateral leg strength, speed, unilateral leg

balance and anthropometric variables.

Mean (±SD) Range Min. Max.

Age 16.6 (± 1.3) 4 15 19

Weight (kg) 76.8 (± 6.6) 24.7 66.0 90.7

Length (cm) 180.5 (± 5.9) 24 174 198

CODS (sec) 4.94 (± 0.15) 0.58 4.71 5.29

SOLEC (sec) 14.51 (± 22.28) 88.54 2.72 91.26

US (kg) 125.0 (± 22.7) 77.5 87.5 165

ULP (kg) 119.2 (± 28.13) 92.5 80.0 172.5

LS5m (sec) 1.05 (± 0.05) 0.22 0.98 1.20

LS10m (sec) 1.78 (± 0.08) 0.32 1.65 1.97

LS20m (sec) 3.07 (± 0.13) 0.52 2.85 3.37

CODS = Change Of Direction Speed, SOLEC = modified Standing on One Leg Eyes Closed (on a

BOSU ball), US = Unilateral Squat (in a Smith machine), ULP = Unilateral Leg Press, LS5m =

Linear Sprint 5 m, LS10m = Linear Sprint 10 m and LS20m = Linear Sprint 20 m.

14

Figure 5. Model shows an overview of the relationship between Change Of Direction Speed

(CODS) ability and unilateral balance ability (SOLEC), linear sprint (5, 10 and 20 m), maximal

unilateral squat strength, maximal unilateral leg press strength and normalized strength (unilateral

squat strength/BM, unilateral leg press strength/BM) for youth male soccer and ice-hockey players

(n=20). ** Correlation is significant at the 0.01 level (2-tailed). *Correlation is significant at the

0.05 level (2- tailed).

3.1 Correlations between CODS and maximal unilateral strength The correlations between various tests are shown in Table 3 and Table 4. Figure 5 shows an

illustration between the relationship between CODS and different tests for soccer and ice-hockey

players (n=20). There were a significant moderately strong correlation between CODS and maximal

strength (Figure 5) in both unilateral Smith machine squat and unilateral leg press (r = -0.662,

P<0.001 and r = -0.579, P<0.007, respectively). When comparing CODS with the normalized

strength variables, unilateral leg press strength was superior to unilateral squat strength (r = -0.631,

P<0.003 and r = -0.606, P<0.006, respectively).

15

Figure 6. Correlation between maximal unilateral squat strength and maximal unilateral leg press

strength respectively, and the test of CODS performance (modified pro agility test) in youth male

soccer and ice-hockey players (n=20) with 95 % confidence interval.

Figure 7. Correlation between maximal normalized unilateral squat strength and maximal

normalized unilateral leg press strength, respectively, and the test of CODS performance (modified

pro agility test) in youth male soccer and ice-hockey players (n = 20) with 95 % confidence

interval.

3.2 Correlations between CODS and linear sprint The relationship between linear sprint and CODS were different depending on distance measured.

The correlation was significant between CODS and 20 m linear sprint and 10 m linear sprint (r =

0.641, P<0.002 and r = 0.629, P<0.003, respectively) but not between CODS and 5 m linear sprint.

r = -0.631

r² = 0.398

P = 0.003

r = -0.606

r² = 0.368

P = 0.006

r = -0.579

r² = 0.335

P = 0.007

r = -0.662

r² = 0.439

P = 0,001

16

Figure 8. Correlation between 10 m linear sprint and 20 m linear sprint, respectively, and the test of

CODS performance (modified pro agility test) in youth male soccer and ice-hockey players (n=20)

with 95 % confidence interval.

3.3 Correlations between linear sprint and maximal unilateral leg strength The relationship between linear sprint to maximal strength in unilateral squat and maximal

unilateral leg press were different depending on distance measured. The correlation was significant

between maximal unilateral squat strength and maximal unilateral leg press strength with 20 m

linear sprint (r = -0.536, P<0.015 and r = -0.485, P<0.030, respectively) and 10 m linear sprint (r = -

0.575, P<0.008 and r = -0.547, P<0.013, respectively) but not between maximal unilateral squat

strength and unilateral leg press strength with 5 m linear sprint. In normalized strength, similar

results were found and a significant relationship between 20 m linear sprint and maximal

normalized unilateral squat strength and maximal normalized unilateral leg press strength (r = -

0.493, P<0.027 and r = -0.514, P<0.020, respectively) and also to 10 m linear sprint (r = -0.534,

P<0.015 and r = -0.593, P<0.006, respectively).

r = 0.629

r² = 0.395

P = 0.003

r = 0.641

r² = 0.411

P = 0.002

17

Figure 9. Correlation between maximal unilateral squat strength test and 10 m linear sprint and 20

m linear sprint, respectively, in youth male soccer and ice-hockey players (n=20) with 95 %

confidence interval.

Figure 10. Correlation between maximal unilateral leg press strength test, and 10 m linear sprint

and 20 m linear sprint, respectively, in youth male soccer and ice-hockey players (n=20) with 95 %

confidence interval.

3.4 Comparing correlations between soccer and ice-hockey players When comparing soccer and ice-hockey players, differences were found between correlations

(Table 5, Table 6, Table 7 and Table 8). There were a statistical significant moderately strong

relationship between CODS and 10 m linear sprint and 20 m linear sprint (r = 0.646, P<0.043 and r

= 0.712, P<0.021, respectively) for soccer players but not between any other variables. For ice-

hockey players the relationship were significance between CODS and maximal unilateral squat

strength and maximal unilateral leg press strength with a moderately strong correlation (r = -0.644,

P<0.044 and r = -0.646, P<0.043, respectively) but not when comparing in normalized strength.

r = -0.485

r² = 0.235

P = 0.030

r = -0.547

r² = 0.299

P = 0.013

r = -0.536

r² = 0.288

P = 0,015

r = -0.575

r² = 0.331

P = 0,008

18

The relationship between linear sprint and different variables also differed depending on the

specific sport. For soccer players 10 m linear sprint correlated significant with CODS (r = 0.646,

P<0.043) but also with the strength tests maximal unilateral squat strength and maximal unilateral

leg press strength and maximal normalized unilateral leg press strength (r = -0.722, P<0.018 and r =

-0.819, P< 0.004 and r = -0.784, P<0.007, respectively). For ice-hockey players 10 m linear sprint

correlated significant with maximal normalized unilateral squat strength (r = -0.663, P<0.037).

There were also a significant correlation for soccer players between 20 m linear sprint and CODS (r

= 0.712, P<0.021) but also with maximal unilateral squat strength, maximal unilateral leg press and

maximal normalized unilateral leg press strength (r = -0.663, P<0.037 and r = -0.703, P<0.023 and r

= -0.666, P<0.035, respectively). For ice-hockey players 20 m linear sprint correlated significant

with maximal normalized unilateral squat strength (r = -0.753, P<0.012).

19

Table 3. Correlation matrix (soccer and ice-hockey, n=20) for strength (mean), speed (mean) and anthropometric variables.

Groups Age Weight Height CODS SOLEC US ULP LS5m LS10m LS20m

Groups 1

Age -0.781** 1

Weight -0.044 0.191 1

Length -0.026 0.104 0.596** 1

CODS -0.410 0.196 -0.216 -0.043 1

SOLEC -0.153 0.275 -0.299 -0.068 -0.235 1

US 0.530* -0.198 0.321 -0.084 -0.662** 0.116 1

ULP 0.292 0.009 0.628** 0.142 -0.579** -0.158 0.653** 1

LS5m -0.194 -0.121 -0.156 -0.223 0.424 -0.223 -0.432 -0.347 1

LS10m -0.215 -0.079 -0.196 -0.090 0.629** -0.133 -0.575** -0.547* 0.907** 1

LS20m -0.078 -0.174 -0.198 -0.086 0.641** -0.283 -0.536* -0.485* 0.876** 0.947** 1

**. Correlation is significant at the 0.01 level (2-tailed).

*. Correlation is significant at the 0.05 level (2- tailed).

CODS = Change of Direction Speed, SOLEC= Standing One Leg Eyes Closed (on a BOSU ball), US = Unilateral Squat (in a Smith machine), ULP =

Unilateral Leg Press, LS5m = Linear Sprint 5 m, LS10m = Linear Sprint 10 m and LS20m = Linear Sprint 20 m.

20

Table 4. Correlation matrix (soccer and ice-hockey, n=20) for normalized strength, speed (mean) and anthropometric variables.

Groups Age Weight Height CODS SOLEC NUS NULP LS5m LS10m LS20m

NUS 0.567** -0.288 -0.147 -0.356 -0.606** 0.282 1 0.550* -0.403 -0.534* -0.493*

NULP 0.392 -0.091 0.305 -0.078 -0.631** -0.056 0.550* 1 -0.362 -0.593** -0.514*



CODS = Change of Direction Speed, SOLEC = Standing One Leg Eyes Closed (on a BOSU ball), NUS = Normalized Unilateral Squat (in a Smith

machine), NULP = Normalized Unilateral Leg Press, LS5m = Linear Sprint 5 m, LS10m = Linear Sprint 10 m and LS20m = Linear Sprint 20 m.

21

Table 5. Correlation matrix for soccer group (n=10) on strength (mean), speed (mean) and anthropometric variables.

Age Weight Height CODS SOLEC US ULP LS5m LS10m LS20m

Age 1

Weight 0.278 1

Length 0.265 0.604 1

CODS -0.177 -0.188 -0.073 1

SOLEC 0.377 -0.374 -0.133 -0.387 1

US 0.442 0.374 -0.084 -0.599 0.149 1

ULP 0.469 0.673* 0.053 -0.483 -0.211 0.765** 1

LS5m -0.603 -0.513 -0.502 0.412 -0.222 -0.553 -0.571 1

LS10m -0.551 -0.542 -0.336 0.646* -0.069 -0.722* -0.819** 0.887** 1

LS20m -0.482 -0.474 -0.348 0.712* -0.211 -0.663* -0.703* 0.912** 0.970** 1



CODS = Change of Direction Speed, SOLEC = Standing One Leg Eyes Closed (on a BOSU ball), US = Unilateral Squat (in a Smith machine), ULP=


22

Table 6. Correlation matrix for the soccer group (n=10) in normalized strength, speed (mean) and anthropometric variables.

Age Weight Height CODS SOLEC NUS NULP LS5m LS10m LS20m

NUS 0.289 -0.244 -0.439 -0.557 0.424 1 0.573 -0.259 -0.423 -0.412

NULP 0.469 0.415 -0.169 -0.543 -0.103 0.573 1 -0.480 -0.784** -0.666*





23

Table 7. Correlation matrix for ice-hockey group (n=10) on strength (mean), speed (mean) and anthropometric variables.

Age Weight Height CODS SOLEC US ULP LS5m LS10m LS20m

Age 1

Weight 0.211 1

Length -0.306 0.595 1

CODS -0.366 -0.414 -0.020 1

SOLEC -0.285 -0.181 0.049 -0.127 1

US 0.465 0.455 -0.093 -0.644* 0.449 1

ULP 0.188 0.677* 0.410 -0.646* 0.157 0.496 1

LS5m 0.112 0.534 0.516 0.308 -0.403 -0.244 0.354 1

LS10m 0.020 0.370 0.468 0.515 -0.490 -0.415 0.134 0.951** 1

LS20m -0.083 0.269 0.519 0.573 -0.579 -0.547 -0.016 0.810** 0.925** 1



CODS = Change of Direction Speed, SOLEC = Standing One Leg Eyes Closed (on a BOSU ball), US = Unilateral Squat (in a Smith machine), ULP =


24

Table 8. Correlation matrix for the ice-hockey group (n=10) in normalized strength, speed (mean) and anthropometric variables.

Age Weight Height CODS SOLEC NUS NULP LS5m LS10m LS20m

NUS 0.397 -0.051 -0.426 -0.480 0.617 1 0.284 -0.565 -0.663* -0.753*

NULP 0.096 0.240 0.154 -0.614 0.335 0.284 1 0.089 -0.099 -0.230





25

4. Discussion

The purpose with this study was to examine the relationship between CODS and linear sprint

to unilateral balance and unilateral maximal (1RM) leg strength in youth male college soccer

and ice-hockey players. Another purpose was to compare if there were differences in

correlations depending on the specific sport. The hypotheses were that maximal unilateral leg

strength would correlate significant with CODS performance and linear sprint and that

unilateral balance would have a weak relationship with all selected tests. CODS and linear

sprint were hypothesized to correlate poorly.

The main results from the study showed that maximal unilateral strength (unilateral squat and

unilateral leg press) correlated significantly with 10 and 20 m linear sprint and CODS, also

when expressed as normalized strength (normalized unilateral squat and normalized unilateral

leg press) for youth male soccer and ice-hockey players. There was a significant moderately

strong relationship between CODS and linear sprint in 10 m and 20 m (r = 0.629, P<0.003 and

r = 0.641, P<0.002, respectively) but not 5 m linear sprint. The unilateral standing balance

test (SOLEC on a BOSU ball) did not correlate significantly with any of the selected

variables.

When the soccer and ice-hockey groups were separated differences were found. For the

soccer group (n=10) a significant moderately strong correlation between CODS and 10 m

linear sprint and 20 m linear sprint (r = 0.646, P<0.043 and r = 0.712, P<0.021, respectively)

was found. For the ice-hockey group (n=10) a moderately strong significant relationship were

found between CODS and maximal unilateral squat strength and maximal unilateral leg press

strength (r = -0.644, P<0.044 and r = -0.646, P<0.043, respectively).

For the soccer group 10 m linear sprint correlated significantly with maximal unilateral squat

strength, maximal unilateral leg press strength and maximal normalized unilateral leg press

strength (r = -0.722, P<0.018, and r = -0.819, P<0.004, and r = -0.784, P<0.007, respectively).

20 m linear sprint correlated significantly with maximal unilateral squat strength, maximal

unilateral leg press strength and maximal normalized unilateral leg press strength (r = -0.663,

P<0.037, and r = -0.703, P<0.023, and r = -0.666, P<0.035, respectively).

For the ice-hockey group 10 m linear sprint correlated significantly with maximal normalized

unilateral squat strength (r = -0.663, P<0.037). 20 m linear sprint correlated significantly with

maximal normalized unilateral squat strength (r = -0.753, P<0.012).

4.1 Correlation between linear sprint and maximal unilateral leg

strength The results of this study are presented in Table 3 and Table 4 and shows there is a moderately

strong relationship between maximal strength in unilateral leg press and unilateral squat to

linear sprint in 10 m linear sprint and 20 m linear sprint even when expressed as normalized

strength. This confirms that maximal lower limb strength is an important factor for linear

26

sprint, however recent studies have focused on bilateral leg strength (Wisloff et al. 2004,

Ronnestad et al. 2008, Chaouachi et al. 2009, McBride et al. 2009, Chelly et al. 2009, Chelly

et al. 2010). This study also shows that unilateral strength is important for linear sprint.

Wisloff et al. (2004) reported a significant strong correlation between maximal (1RM)

bilateral half squat (90˚ in knee flexion between femur and tibia) and 10 m linear sprint and

30 m linear sprint (r = 0.94 and r = 0.71, respectively) when testing 17 international male

soccer players. Chaouachi et al. (2009) also tested maximal (1RM) bilateral half squat

strength and found a significant relationship to linear sprint 5 m, 10 m and 30 m (r = -0.63 and

r = -0.68 and r = -0.65, respectively) and the best correlation were found to linear 5 m sprint

when examining 14 elite professional basketball players. Cronin and Hansen (2005) tested 26

part-time and full-time professional rugby league players and found no significant correlation

between maximal (3RM) squat strength and 5 m, 10 m and 30 m sprint times. Rugby players

usually are heavier than for example soccer players, which could explain the results. In this

study we found no significant correlation between 5 m linear sprint and maximal (1RM)

unilateral strength. This was unexpected because earlier studies have reported that maximal

strength is important in the first 5 m, although we found no earlier studies tested the unilateral

strength in maximal unilateral leg press and maximal unilateral Smith machine squat. The

results could be affected by inexperience in sprinting technique or the fact that no power

measures were used in the study.

This confirms that maximal lower limb strength is important for linear sprint in intermittent

sports.

4.2 Correlation between CODS and linear sprint A statistically significant correlation was also found between CODS and linear sprint in the

distances 10 and 20 m linear sprint (r = 0.629, P<0.003 and r = 0.641, P<0.002, respectively)

but not 5 m linear sprint. The results of our study are not in line with earlier studies (Little &

Williams, 2005, Wisloff et al. 2004, Chaouachi et al. 2009), which has reported low

correlations between CODS and linear sprints. Chaouachi et al. (2009) examined 14

professional elite male basketball players and the relationship between CODS (T-test) and

linear sprint (5, 10 and 30 m) and found no significant correlation. Why we found a

correlation between CODS and linear sprint could be due to the fact that different CODS tests

used were T-test which consist of acceleration, deceleration, lateral stepping and backward

running and is a more complex test than our modified pro agility test which does not include

lateral stepping and backward running. The modified pro agility test is further similar to linear

sprint compared with the T-test. There were also a difference in Chaouachi et al. (2009) study

were less participant attended as well as a shorter rest period, two to three minutes between

the trials compared with this study (five minutes). Fatigue may have influenced the test

results.

Little and Williams (2005) examined a large sample consisting of 106 professional soccer

players and the relationship between CODS (zigzag agility test) and 10 m sprint (acceleration)

and flying 20 m sprint (maximum speed). The results showed that acceleration, maximum

speed and CODS are specific qualities and thus unrelated. Although a Little & Williams

27

(2005) used a large sample only a significantly moderately low correlations were found. This

could be due to the differences in selection of CODS test were zigzag agility test require

acceleration and changes of direction speed, and the pro agility test require acceleration,

deceleration and 180° turns.

The modified pro agility test is a relevant test for both soccer and ice-hockey which constantly

requires high intensity acceleration, deceleration and 180˚ turns during game performance,

which could explain the significant results. CODS are a complex activity and there are

differences in CODS tasks depending on the sport.

Results on the relationship between CODS and linear sprint are not consistent. We found a

correlation between CODS and linear sprint, however these correlations seems to depend on

which type of CODS test and to the population tested.

4.3 Correlation between CODS and maximal unilateral strength The study shows a significant relationship between CODS and maximal strength in unilateral

leg press and unilateral squat and also in normalized strength. Earlier studies which tested the

bilateral strength have failed to report a significant relationship to CODS (Chaouachi et al.

2009, Markovic, 2007, Markovic et al. 2007). In Markovic (2007), 76 physical education

students performed three different CODS tests including 20 yard shuttle run and six leg

extensor strength tests including maximal (1RM) bilateral back squat strength in a Smith

machine but did not found any significance between strength and CODS. The best correlation

was found between the functional test one-leg rising test (r = 0.31) and CODS. In the study by

Markovic (2007) a large sample group of physical education students were used with

backgrounds in both individual and team sports which could have affected the results because

the lack of specificity in the tests to the population. In this study we used the modified pro

agility test (also called 20 m shuttle run) which is very similar to the 20-yard shuttle run used

in Markovic (2007) study and we found a significant relationship. This could be due to the

specificity in selection of exercise to the tested population. Bilateral back squat in a Smith

machine does not require a high degree of balance and stability and is not specific to

intermittent CODS sports.

A study by Chaouachi et al. (2009) examined the relationship between maximal (1RM)

bilateral back squat strength with free weights and a basketball relevant CODS test (T-test) in

fourteen elite male professional basketball players. The results showed no significant

correlation between 1RM back squat strength and the CODS test, although a CODS test

relevant to basketball were used as well as back squat performed with free barbells. Despite

performing bilateral back squat with free barbells which require more balance and stability no

significant correlation was found. The results from this study prove there are differences

between bilateral and unilateral leg strength exercises and the relationship to CODS and the

findings of this study shows the importance of unilateral leg strength in intermittent sports.

According to the authors of this study the reason why this study found a significant

relationship between maximal lower limb strength and CODS were due to the fact that most

28

CODS tasks is often performed and developing power on one leg at the time and strength

should therefore be tested as such. Unilateral squat is a complex exercise to perform, which

requires maximal lower limb strength, stability and balance which seems to be a good

predictor for CODS performance. Unilateral leg press strength was also significant correlated

(r = -0.579, P<0.007) to CODS although it is a less complex exercise but still require the

participant to develop force on one leg.

The highest measured correlation with CODS was with maximal unilateral squat strength (r =

-0.662, P<0.001, Figure 6). Significant correlations was also found between CODS and

normalized strength (maximal unilateral squat and maximal unilateral leg press, r = -0.606,

P<0.006, r = -0.631, P<0.003, respectively), in line with Newton’s second law of motion the

acceleration is affected by force and body mass (Figure 7). These results show the importance

of complexity in exercise selection and unilateral normalized strength when testing for CODS.

4.4 Correlation between CODS and linear sprint to unilateral balance

ability As suggested by Markovic (2007) agility is a complex activity and balance could be a part

that determines agility performance, and therefore we tested the modified SOLEC on a BOSU

ball and the relationship to linear sprinting and CODS. During a standard SOLEC test, the

participant standing on one leg and eyes closed on a flat surface. To increase the sensitivity of

this test when it came to the young, healthy and well trained subjects in this study we choose

to modify the level of difficulty by using a BOSU ball. The results revealed no significant

results to any of the selected tests. The unilateral balance test (modified SOLEC on a BOSU

ball) was not a good predictor for either CODS or linear sprint for youth male soccer and ice-

hockey players. This was in line with our expectations; however balance is probably still an

important ability in CODS which involve unilateral balance in changes in direction in high

speed. Yaggie and Campbell (2006) four week unilateral standing balance study showed a

significant improvement in a CODS test which suggest that unilateral balance have some

transfer value to CODS. In the present study a more specific test for balance ability and a

larger number of participants might show different results.

4.5 Differences between soccer and ice-hockey Even though both soccer and ice-hockey classifies as intermittent sports with lots of CODS

activities, they are still requiring very different movements within each sport. The results

indicate there are differences between the sports when comparing the relationship between

CODS and the selected tests. For the soccer group (n=10) CODS correlated significantly (r =

0.646, P<0.043, r = 0.712, P<0.021, respectively) with 10 m linear sprint and 20 m linear

sprint, whereas the ice-hockey group (n=10) showed a significant relationship between CODS

and maximal unilateral squat strength and maximal unilateral leg press strength (r = -0.644,

P<0.044, r = -0.646, P<0.043, respectively) but not when comparing in normalized strength.

This could be explained by the large difference in the foundation of the specific sports where

ice-hockey is performed on ice and soccer on grass and therefore the soccer players are more

29

accustomed to the sprinting activities. Soccer naturally requires running activities while ice-

hockey requires skating activities to perform different activities on a low friction foundation.

There were also differences between the sports and the relationship between linear sprint and

the selected tests. For the soccer group 10 and 20 m linear sprint correlated significant with

maximal unilateral squat strength, maximal unilateral leg press strength and in normalized

strength. For the ice-hockey group 10 m linear sprint and 20 m linear sprint significantly

correlated only with maximal unilateral squat in normalized strength. This could probably be

explained by the low sample consisting of only ten participants in each group. A limitation in

the comparison between soccer and ice-hockey is that the results only reveal a difference in

correlation but not if it is significant, therefore it is not possible to make any conclusions. The

results could be observed as differences between correlations but cannot compare the results

due to the fact that random may have influenced.

4.6 Limitations The results are in line with Sheppard & Young’s (2006) universal model of agility which

suggests that CODS performance depends on straight sprinting speed, technique, leg muscle

qualities and anthropometrics. Our results confirm a significant relationship between CODS

and linear sprint in 10 and 20 m and maximal unilateral leg strength and normalized strength.

The results confirm the theory that intermittent sports require strength performed unilaterally,

however it still require more studies to confirm the relationship. These results are based on

youth male soccer and ice-hockey players, it still require more studies to confirm this results

and if the same relationship exists in other intermittent sports.

A limitation of this study is the small sample size. The sample size consisted of twenty soccer

and ice-hockey players to see if correlations were found between maximal unilateral strength

exercises to CODS and linear sprint. When separating soccer and ice-hockey in to two

different groups there were less significant results suggesting that a larger sample size is

needed. In the present study it was not possible to see if there existed a statistically significant

difference between the groups. The results shows a difference and future studies should be

performed with a larger sample size to confirm our findings and allow for more predictor

variables to be included in the analysis and to examine differences in intermittent sports.

The standardization of the tests are an important aspect of studies and the selection of strength

tests were based on the assumption that specificity is important when examining sports and

that intermittent sports often require to develop force and power unilaterally. The unilateral

squat performed with free weights is an advanced exercise with a higher risk of injury, and to

further increase the reliability we chose to conduct the test in a Smith machine. To standardize

the testing procedures the depth of the squat were 90° in knee flexion (between femur and

tibia). To ensure the right depth an elastic exercise band was attached to a rack (Figure 4)

behind the participant. The unilateral leg press were standardized in a different knee angle

where the participant were instructed to lower the weights until the thigh were parallel with

30

the foot platform. The reason was to ensure the reliability because there were easier to make

sure the participants attained the same depth.

The linear sprint test consisted of 20 m where timing gates were placed on 5 m, 10 m and 20

m to minimize the effects of fatigue. A flying start of 50 cm was used to eliminate the reaction

time and unexpected initiation of the timing. The testing procedures consisted of five different

tests on the same day and to minimize the effects fatigue the resting periods of five minutes

between the different tests were used.

The reason only youth male athletes were included in the study was because the results could

be applicable to the largest population possible. Another reason why only youth male athletes

were chosen was due to limited population of active youth female ice-hockey players.

As no standardised protocol for testing strength of either soccer or ice-hockey players exists,

as well as the test unilateral Smith machine squat have not been used in this particular

research question, it is difficult to compare the results among different studies. In our view,

intermittent sports are complex and require different activities in its nature and logically the

testing procedure should mimic and try to capture the complexity of the movements.

Isokinetic tests and strength test performed bilaterally do not test the sport specific strength in

sports like soccer and ice-hockey which often develop force on one leg at a time, and

therefore testing unilateral strength should be a better predictor of CODS.

31

5. Conclusion

It is a challenge for strength and conditioning coaches to find exercises which has a high

transfer value to a given sport. There is often a time limit where strength and conditioning

coaches have to prioritize exercises that contribute to the specific sport, and due to the limited

amount of time available for strength training, the strength and conditioning coaches have to

be able to choose the training exercise with the most transfer value to the sport. For training to

be effective exercise selection should have a high transfer value to sport specific activities,

and knowledge on unilateral and sport specific training needs to be further examined.

The results of this study suggest that maximal unilateral multi-joint leg strength is important

and a good predictor in linear sprint in 10 and 20 m and CODS performance in youth male

soccer and ice-hockey players.

Earlier studies have found a significant relationship between maximal bilateral squat strength

and linear sprint but not to CODS. In the present study we found a significant relationship

between maximal unilateral strength and linear sprint and CODS suggesting CODS is a more

complex activity and require strength development unilaterally.

Earlier studies have struggled to find a significant relationship between maximal leg strength

and CODS performance and it appears as a more functional and specific approach should be

used. Unilateral squat represents a complex functional strength test that requires producing

power and force in one leg at a time and seems to be a good predictor of CODS performance

in soccer and ice-hockey players. Even maximal unilateral leg press strength were a good

predictor of CODS even though it represent a lesser complex task but still require to produce

unilateral leg strength.

Strength and conditioning coaches and sport scientists who work with intermittent sports

should be aware of the fact that maximal unilateral squat strength and maximal unilateral leg

press strength are good predictors of CODS and linear sprint performance. Unilateral

resistance training could be a method for increasing linear sprint and CODS performance for

soccer and ice-hockey players.

Future studies should examine the relationship between CODS and unilateral strength to

different CODS tests and sports to increase the reliability. Intervention studies examining the

difference between bilateral and unilateral strength training to CODS performance are needed.

32

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Appendix Informed consent form 1(1)

Informerat dokumenterat samtycke

Syftet med studien är att se eventuella samband mellan maximal styrka i benmuskulaturen utfört på ett

ben, balans och enbensknäböj i Smith-maskin, med Change of direction speed (snabbhet i

riktningsförändringar) och linjär sprint (5 m, 10 m, 20 m).

Det som förväntas av dig som testperson är att genomföra ett familijäriseringstillfälle och ett

testtillfälle. Dessa tillfällen består av mätningar bestående av vikt, längd, balanstest och agilitytest.

Efter dessa test utförs två styrketest på ett ben bestående av maxstyrketest i benpress i en ben press och

enbensknäböj i en Smith-maskin.

Familijäriseringstillfället tar totalt ca 60-90 minuter och testtillfället tar totalt ca 60-120 minuter.

Testerna och familijäriseringen kommer att äga rum i Friidrottens hus, Göteborg. Samtliga tester

instrueras och övervakas noggrant av tre testledare.

Inklusionskriterierna för deltagande i studien är att vara aktiv inom alltingen ishockey eller fotboll de

senaste fem åren och styrketräningserfarenhet gällande sin sport. Deltagarna skall vara inom åldrarna

15-19 år. Deltagarna får inte ha någon nuvarande skada eller lida av någon pågående

infektionssjukdom som kan påverka testresultaten.

Deltagarnas personuppgifter och resultat kommer att behandlas helt anonymt och endast användas i

studien.

Deltagande i denna studie är helt frivilligt och kan avbrytas när man så behagar. Deltagande i denna

studie möjliggör ny forskning som kan leda till nya träningsmetoder och en modern utveckling av

deltagarens idrott.

Jag intygar att jag har tagit del av vad undersökningen går ut på och accepterar att frivilligt ställa upp

som testperson. Jag säkerställer här med också att jag inte har någon nuvarande skada eller lider av

någon pågående infektions sjukdom som kan påverka testresultaten.

Datum och underskrift________________________Namnförtydligande________________________

Tack för ditt deltagande!

Anton Arin, Daniel Jansson och Kristian Skarphagen

Idrottsvetenskap - Sport Coaching med inriktning fysiologi, Göteborgs Universitet

37

Information to participants 1(2)

Information till deltagare i studien:

Maximal styrka på ett ben korrelerar med linjär

sprint och snabbhet i riktningsförändringar

Bakgrund

Tidigare forskning har hittat ett samband mellan styrka i benmuskulaturen och linjär sprint på

distanser mellan 0-20 m. Man har även försökt hitta ett samband mellan agility och styrka i

benmuskulaturen, men misslyckats. Tidigare forskning har framförallt fokuserat på två ben, i

isokinetiska maskiner och oftast isolerade övningar. Lite forskning har utförts på styrka på

korrelationer mellan styrka på ett ben, agility och linjär sprint. Med tanke på att de flesta lagidrotter

utförs i huvudsak på ett ben i taget är det intressant att se korrelationer till agility och linjär sprint.

Syfte

Syftet med studien är att se eventuella samband mellan maximal styrka i benmuskulaturen och balans

utfört på ett ben med agility (snabbhet i riktningsförändringar) och linjär sprint (5, 10 och 20 m).

Projektets upplägg

Testningen sker under ledning av tre idrottsvetenskapsstudenter med erfarenhet av styrketräning och

styrkemätning, som skriver sin kandidatuppsats. Du som deltar i projektet kommer genomgå test av

maximal styrka i liggande benpress utfört på ett ben, enbensknäböj i Smith-maskin, ett balanstest på

BOSU-boll, sprinttester på upp till 20 m samt ett agility-test. Under testerna kommer vi mäta

testpersonernas sprint- och agility tider med hjälp av fotoceller och dataprogrammet MuscleLab, samt

den maximala kraftutvecklingen i ett ben. Studien sker vid Friidrottens Hus, Göteborg.

Betydelse

Resultaten av denna studie ska ligga till grund för ökad kunskap om träningsmetoder för

idrottsspecifika rörelsemönster.

Vad innebär medverkan i projektet?

All testning är kostnadsfri. Du kommer att kallas till sammanlagt två testtillfällen (beräknad tidsåtgång

är ungefär 60-120 minuter per tillfälle). Tag med träningskläder (shorts och t-shirt) och

gymnastikskor. Du kommer att få tillfälle att genomföra tester som är väldigt relevanta inom din

idrott, med en högteknologisk och exklusiv testutrustning.

Du får inte genomföra någon ansträngande fysisk träning som involverar benmuskulaturen dagen

innan testtillfället.

Lokal

Friidrottens Hus, Mikael Ljungbergs Väg 10, 414 76 Göteborg.

38

Information to participants 2(2)

Fördelar och risker med att delta i studien

Risker

Att delta i studien kräver lite tid och uppmärksamhet från din sida, det krävs att du är

tillgänglig vid två tillfällen. Testprotokollet som genomförs är maximala tester som kan

medföra muskelsmärta (träningsvärk) dagarna efteråt. Testerna kan också uppfattas som

ansträngande.

Fördelar

Du har möjlighet att delta i ett spännande och nytänkande forskningsprojekt som kan utmynna

i ny kunskap om idrottsspecifik träning. Som deltagare har du möjlighet att ta del av

information samt praktiskt utöva de senaste inom forskningen angående

styrketräningsmetoder med hjälp av högteknologisk utrustning som annars skulle vara väldigt

kostsamma att genomföra. Alla som deltar i studien kommer att vara anonyma i arbetet. Alla

som deltar i studien kommer vid projektets slut få resultat av studien presenterat i form av ett

utskrivet exemplar av examensarbetet. Dessutom är man välkommen att lyssna på vår

presentation av projektet.

Rätten att avbryta medverkan i projektet

Deltagandet i projektet är helt frivilligt.

Om Du undrar över något är Du välkommen att ringa någon av oss i projektgruppen.

Idrottsvetenskapsstudent Idrottsvetenskapsstudent

Kristian Skarphagen, tel: 073-3447495 Daniel Jansson, tel: 073-0568128

Idrottsvetenskapsstudent Leg. Sjukgymnast, med dr, handledare

Anton Arin, tel: 073-6728226 Jesper Augustsson, tel: 031-7862237

39

Figures 1(4)

Figures for the soccer group, n=10 (absolute strength):

40

Figures 2(4)

Figures for the soccer group, n=10 (normalized strength):

41

Figures 3(4)

Figures for the ice-hockey group, n=10 (absolute strength):

Figures for the ice-hockey group, n=10 (normalized strength):

42

Figures 4(4)

Figures for soccer and ice-hockey players, n=20 (normalized strength):

maximal unilateral leg strength correlates with linear sprint and … · 2013-04-24 · title (in...

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